Windows: Add Key_Backtab as possible key combination for Shift+Tab

In windows Backtab key event always comes as "Shift+Backtab".
So in order for Backtab key to be recognized as a shortcut sequence,
we also consider Backtab without shift modifier a possibility.

Fixes: QTBUG-94890
Change-Id: I20a7b404b57d8df5bea23765257a178f2e098ed0
Pick-to: 6.8
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/windows/qwindowskeymapper.cpp

@@ -1354,6 +1354,11 @@ QList<QKeyCombination> QWindowsKeyMapper::possibleKeyCombinations(const QKeyEven
         return result;
     }
 
+    // If Key_Tab+Shift is pressed we add Key_Backtab without
+    // shift modifier as a possible combination too
+    if (baseKey == Qt::Key_Tab && (keyMods & Qt::ShiftModifier))
+        result << (Qt::Key_Backtab | (keyMods & ~Qt::ShiftModifier));
+
     // The base key is _always_ valid, of course
     result << QKeyCombination::fromCombined(int(baseKey) + int(keyMods));
 

tests/manual/shortcuts/main.cpp

@@ -102,6 +102,8 @@ void ShortcutTester::setupLayout()
         Qt::ControlModifier | Qt::Key_BracketRight,
         Qt::ShiftModifier | Qt::Key_F3,
         Qt::ControlModifier | Qt::Key_F3,
+        Qt::Key_Backtab,
+        Qt::ShiftModifier | Qt::Key_Backtab,
     };
 
     for (const auto k : keys3)